1. Technical Field
The present invention relates to a technique for reducing display defects on a liquid crystal panel.
2. Related Art
A liquid crystal panel has a configuration in which a liquid crystal is interposed between one pair of substrates maintained so as to be separated from each other by a constant gap. Described in detail, the liquid crystal panel has a configuration in which pixel electrodes for pixels are arranged in a matrix pattern on one substrate, a common electrode is disposed so as to be common to the pixels on the other substrate, and a liquid crystal is interposed between the pixel electrodes and the common electrode. When a voltage according to a gray scale level is applied and maintained between the pixel electrode and the common electrode, the alignment state of the liquid crystal is defined for each pixel, and thereby the transmittance or the reflectance is controlled. Thus, in the above-described configuration, only a component of an electric field applied to liquid crystal molecules in a direction from the pixel electrodes to the common electrode (or in the opposite direction), that is, in a direction perpendicular to a substrate surface (vertical direction) contributes to display control.
However, in a case where the pixel pitch has become narrow due to a recent trend of reduction in size and higher precision, an electric field that is generated between pixel electrodes adjacent to each other, that is, an electric field is generated in a direction parallel to the substrate surface (lateral direction), and the effect thereof is becoming such that it is no longer negligible. For example, if a lateral direction electric field is applied to a liquid crystal to be driven by a vertical electric field, such as a VA (Vertical Alignment) type or a TN (Twisted Nematic) type, a defect in the alignment of the liquid crystal (that is, reverse tilt domain) occurs, thereby causing a display defect.
In order to reduce the effect of the reverse tilt domain, a technique of contriving the structure of a liquid crystal panel, for example, by defining the shape of a light shielding layer (opening portion) in accordance with the pixel electrodes (for example, see JP-A-6-34965 (FIG. 1)), a technique of clipping a video signal having a set value or more based on a determination that the reverse tilt domain occurs in a case where the average luminance value calculated from video signals is equal to or less than a threshold value (for example, see JP-A-2009-69608 (FIG. 2)), and the like are proposed.
However, according to the technique of reducing the reverse tilt domain by means of the structure of the liquid crystal panel, the aperture ratio can be easily decreased. Furthermore, there is a problem in that it is difficult to apply the technique to a liquid crystal panel that has already been manufactured without taking the structure thereof into account. On the other hand, according to the technique of clipping a video signal having a set value or more, there is a problem in that the brightness of a displayed image is limited to the set value.